Fracture of Epoxy Matrixes Modified with Thermo-Plastic Polymers and Winding Glass Fibers Reinforced Plastics on Their Base under Low-Velocity Impact Condition

Fracture Toughness of Winding Carbon Plastics Based on Epoxy Matrices and Reinforced by Polysulfone Film

In this work, the fracture mechanism of winding carbon-fiber-reinforced plastics (CFRPs) based on epoxy matrices reinforced by polysulfone film was investigated. Two types of polymer matrices were used: epoxy oligomer (EO) cured by iso-methyltetrahydrophthalic anhydride (iso-MTHPA), and EO-modified polysulfone (PSU) with active diluent furfuryl glycidyl ether (FGE) cured by iso-MTHPA. At the winding stage, the reinforcing film was placed in the middle layer of the CFRP. The fracture toughness GIR of the obtained CFRP was determined by the double-cantilever beam delamination method. Additionally, the effect of cyclic loading on the fracture toughness of CFRP reinforced with polysulfone film was investigated. It was shown that heterogeneous structures arising from the dissolution of the polysulfone film in the epoxy binder during the curing process increase the fracture toughness of CFRP from 0.5 kJ/m2 to 1.2 kJ/m2. Application of cyclic loads had little effect on the fracture toughness value. As a result of this study, it was revealed that the macrocrack propagates near the reinforcement layer along the diffusion zone, which has a phase organization of the type PSU matrix-EO dispersion.

The Influence of Residual Stresses on the Curve Shape-Describing Interface Behavior in "Polymer-Fiber" Systems

The pull-out method was used to study the adhesive strength τ of "fiber-thermoset" systems with wide variations in area. Studied binders were based on resins that had different chemical natures (epoxy, epoxy phenol, orthophthalic, polyphenylsiloxane, and phenol-formaldehyde). Shear adhesive strength was determined for systems with two fiber types (glass and steel fibers). It was shown that strength τ depended on scale (area). Formation of τ occurred during the curing process and the system's subsequent cooling to the measurement temperature T. It was found that interface strength depended on measurement temperature across a wide temperature range that covered the highly elastic and the glassy state of the adhesive. The influence of residual stresses τres, acting at the "binder-fiber" interface, on the nature of the curves describing the dependence of the adhesive strength on the studied factor was experimentally shown. A qualitative explanation of the observed regularities is proposed.